A total solar eclipse began its flight across a narrow path of Asia today, where it was expected to darken the skies for millions of people for more than six minutes in some places.
The longest total solar eclipse of the 21st century will be visible in a roughly 250 km-wide corridor, according to the US space agency NASA, as it travels half the globe and passes through the world's two most populous nations, India and China.
The eclipse began at 5:28 a.m. local time (2358 GMT) in India and will last up to a maximum of 6 minutes, 39 seconds when it hits the Pacific Ocean, according to NASA.
Eclipses allow earth-bound scientists a rare glimpse at the sun's corona, the gases surrounding the sun.
Starting on India's west coast north of financial capital Mumbai, it took in the ancient Hindu holy city of Varanasi on the Ganges river.
Tens of thousands of people snaked through the narrow lanes of Varanasi and gathered for a dip in the Ganges, an act considered to lead to salvation from the cycle of life and death.
Amid chanting of Hindu hymns, men, women and children waded into the river with folded hands and prayed to the sun as it emerged in an overcast sky.
"We have come here because our elders told us this is the best time to improve our after-life," said Bhailal Sharma, a villager from central India, who came to Varanasi with a group of about 100 people.
The eclipse was due to sweep through Bangladesh, Nepal, Bhutan, Myanmar and China's financial hub Shanghai, before heading to the Pacific.
"In the 21st century this is the longest," said Harish Bhatt, dean at the Bangalore-based Indian Institute of Astrophysics.
"This is indeed quite an important event for scientific experiments. Its long duration provides you an opportunity to make very complicated, complex experiments."
MIXED BLESSING
Scientists in China will be snapping two-dimensional images of the sun's corona -- up to 2 million degrees celsius hot -- at roughly one image per second, Bhatt said.
The eclipse is seen as a mixed blessing for millions of Indians. Crowds across the country will bathe in holy rivers and ponds for good fortune as they consider the solar blackout auspicious.
But according astrologers' predictions, the eclipse spells bad luck for others and expectant mothers have asked doctors to advance or postpone births, fearing complications or a miserable future for their children.
Parents in several schools in India's capital, New Delhi, said they would not send their children to class as the eclipse coincides with breakfast. According to Hindu custom, it is inauspicious to prepare food during an eclipse.
In ancient Chinese culture, an eclipse was a bad omen and linked to natural disasters or deaths in the imperial family. Chinese officials and state media have been at pains to reassure the public that city services will run normally.
But in modern China, people who want to see the astronomical rarity may have to escape thick pollution caused by the rapid industrial growth, which smudges the horizon, even on clear days.
"The majority of people decided to go to Tongning, in Anhui, because they're worried about the serious air pollution from industrial areas in Shanghai," said Bill Yeung, the president of the Hong Kong Astronomical Society, who organised a trip by 120 eclipse watchers from Hong Kong.
Tongning has an 80 percent chance of clear skies, while Shanghai's is only 10 percent, he said.